Ink cartridge with residual ink retaining structure

Abstract

An ink cartridge connectable to a print head having a supply pipe which receives a supply of ink includes a casing having a first, upper chamber and a second, lower chamber communicating with each other via a communicating hole and storing the ink, a porous body provided in the first chamber and storing the ink by a negative pressure, and a connection part provided in the second chamber and connectable to the supply pipe. The connection part has normally closed valve means for communicating the print head with the second chamber by opening when the supply pipe is inserted into the connection part. The ink cartridge includes a connecting pipe extending from the first chamber into the second chamber and a filter member covering the opening of the connecting pipe in the second chamber. The filter member releases air from the connecting pipe upwardly into an upper region of the second chamber.

What is claimed is: 
     
       1. An ink cartridge for connecting to a print head having a supply pipe for receiving a supply of ink from said cartridge, comprising: a casing having a partition dividing the interior of said casing into a first chamber, and a second chamber disposed below said first chamber,   a connecting pipe attached at a first end to said partition and having a second end extending into a lower region of said second chamber,   a hole in said partition opening upwardly into said first chamber and downwardly into the interior of said connecting pipe,   an opening adjacent the second end of said connecting pipe and opening upwardly into said second chamber to establish communication between the interior of said pipe and said second chamber,   a porous body in said first chamber operative to store ink therein at a negative pressure,   a filter member covering said opening at said second end of said connecting pipe, said filter member developing a meniscus force operative to compensate for decreases in an ink retaining capacity of said porous body in said first chamber and being effective to release upwardly into an upper region of said second chamber air generated in the interior of said connecting pipe from a reduction in negative pressure of said porous body whereby said meniscus force in said filter member is augmented, and   a connection part communicating with said second chamber and operable for detachable connection to said supply pipe.   
     
     
       2. The ink cartridge as claimed in claim 1, further comprising a plurality of electrodes in said second chamber operative to detect a residual quantity of ink. 
     
     
       3. The ink cartridge as claimed in claim 2, wherein said plurality of electrodes are disposed at predetermined positions in said second chamber such that, when ink is detected as having run out, a quantity of the ink that actually remains in said second chamber is sufficient to print at least one page. 
     
     
       4. The ink cartridge as claimed in claim 1, wherein said filter member is made of a #30 to #80 mesh. 
     
     
       5. The ink cartridge as claimed in claim 1, wherein said filter member is made of a material providing a contact angle greater than 5 degrees with respect to the ink. 
     
     
       6. An ink cartridge as claimed in claim 1, wherein said connection part includes a normally closed valve means for selective connection of said print head with said second chamber when said supply pipe is inserted into said connection part. 
     
     
       7. An ink cartridge according to claim 6, wherein said valve means includes a packing having an opening enabling said supply pipe to enter said second chamber when said ink cartridge approaches said print head, a valve body having a convex hemispherical surface effective to cooperate with a concave hemispherical surface forming a seat in said packing, and a spring urging said valve body against said seat whereby a gap is prevented from being created between said supply pipe and said valve body when said valve body is moved by said supply pipe. 
     
     
       8. The ink cartridge as claimed in claim 7, wherein said valve body and said packing are made of a resilient material having a hardness of 40 degrees to 70 degrees.